To become better at drawing, you can start by drawing a lot because the more you do it, the more perfect you become. The other thing you can do is to ensure you draw slowly and steadily whether you are using a brush, pencil or crow quill. You can start by drawing slowly so as to have control over what you are doing on the paper and then increase speed as you proceed. You can also get better by learning from the best especially from the artists that you admire. Ask them questions on how to draw different things better. You should also fix your drawing until it is right especially when working on a difficult piece; redraw it until you get it right. Study the best books and watch videos on perspective, anatomy, construction, rendering and color theory and finally look out to learn more as there is a lot to be learnt out there with regards to drawing.
Pracice get a few how to books and study other peoples work if you're looking to draw people there are a lot of great bases to look at and show you how different poses are.. Also there are gazillions of tutorials everywhere.... Try deviant art there are some pretty cool things there